Pulp and fiber product and process of making same



Patented June 18,1929.

UNITEDIJSTATES 1,717,794 PATENT OFFICE.

' Io Drawing.

.The present invention relates to the production of fiber, pulp, and paper. by the use of a particular class of treating liquids which have not heretofore been employed in the manufacturing of pulp from wood or other vegetable materials so far as I have been advised.

In my U. S. patent application No. 407,- 759, filed September 2, 1920, of which the present case is in part a continuation, I have described and claimed the process of making pulp by treating organic materials containing cellulose, wit'i digestive solution containing copper sulfate, iron sulfate, or with other sulfates such as those of cobalt, nickel, manganese and chromium, and said 'application'also mentioned the use of double sulpliatesofcertain metals with the sulfatesof the-alkali metals,-and magnesium sulfate is also mentioned therein.

The present invention is-in its more s e cific aspect based upon the use of a sol'u 1e sulfate of an alkali-forming metal (i. e., alkali sulfate or magnesium sulfate) as the principal constituent. of the digestive solution although it is to be understood that such sulfates can be used in conjunction with other metabsulp'hates as will appear below. In its broader aspect, the present case involves the use of a digestive solution including a sulfate of a metal having an atomic weight between 23 and 63.6, such solution being preferably of a concentration of about 0.5 to 5 ounces (preferably below 4 ounces) per gallon, such solution being much more dilute than the digestive solutions heretofore generally employed in this country.

Among the prior processes, it 'may be noted that there is a so-called sulphate process, which is a somewhat incorrect name, since in the said sulphate process the alkali metal sulfate employed is, before it is used for the digestion of the wood, ordinarily in large part reduced to the corresponding snlfid, and a solution of the sodium sulfid or other alkali metal sultid, usually also containing considerable free alkali, forms the real digestive solution. In my process, I use no alkali metal sulfid and no free caustic alkali.

In the present process it is possible to successfully employ the solutions of alkali metal sulphate which are very much less concentrated than are the. ordinary cooking liquors used in the manufacture of pulp, for example, I find that a strength of from one BOBEF'I A. NLRB, OF NORFOLK,

rim? AND rnma rnonuc'r AND rnocass or name sum. 1

. a lic tion m February z, 1923. Serial at. 816,609.

to four ounces (preferably about one and one-half ounces to three ounces) of the .sulphate results. Further this liquor,at the end of the cooking operation, after separation from the cooked chips or cooked wood in blocks or other cellulosic material can be put back into the digester and used again with another batch of chips or blocks The digestive liquor can be used over many times, but

it is advisable to add to the liquor from time per gallon of liquor gives excellent to time, say after every fourth, or fifth cook, an amount of the sulfate equal to a minor fract-1on,s'ay about one-fourth of the amount origlnally employed.

I give the following examples of proced-- ure falling within the scope of the invention, but it is to be understood that these examples are given as illustrative and not as restrictive.

Example 1. White birch was cut into chips, averaging about one-half a cubic inch in size. The

chips in this particular example were packed in a cage and the cage then placed in the digester, with a solution containing 1.8 ounces per gallon (1.4%) of sodium sulphate alone. An amount of digestive solution equal to about seven gallons of the said solution per ten pounds of wood was added, this being suflicient to completelycoiler the said chips. The liquor was then heated, until the steam pressure in the digester was about 100 pounds per square inch, which condition was maintained for about 60 min utes. The source of heat was then shut off and the liquor in the digester allowed to 0001 until the pressure in the digester had dropped to 60 pounds. The relief valve of the digester was then slowly opened, the digester opened, and the cage of chips was removed from the digester. The chips, after rinsing with cold water, were run through a kollar-gang with water, and were then run into a beater engine, in which the roll was raised a considerable distanceabove the bed. The. pulp was beaten with water, gradually lowering the roll until at the end. of the beating operating, which occupied about 60 minutes, the roll was about onehalf turn up from the bed.

The beaten material was then run direct onto a screen and separated from the water, without any washing, and then the sheets were dried. This produced a pulp of relahaving a thickness of .0022 inches was found turns u to have a'breaking strength of 20 pounds (Mullen test). Another sheet, having a.

thickness of 0.2 inch, had a Mullen test of 500 pounds. This is really a plastic wood, as nothing whatever has been added, the

product being apparently the full contents of the wood with the exception of the sugars and other soluble constituents.

By the procedure above described it is possible to convert the raw wood into finished products and sheeted pulp in less than three or four hours. Numerous tests which I. have made indicate'a yield substantially better than 90% based on the dry weight of the wood used.-

The resulting paper in this example was of a yellowish or brownish color, somewhat darker than the ordinary manila stock, very well suited for'wrapping paper on account of its high strength.-

In other similar tests, blocks of wood, up to 150 cubicinches' in size have been used in place of chips as above referred to, these being cooked about an hour or even an hour and a half, at 100 unds pressure, with the solution as above escribed.

' Example 2.

VVhitespruce was cut into chips averaging about-three-fifths; of a cubic mob in size. These chips were digested in. a solution containing about 1.4 ounces of sodium sulphate and about .3 ounces of cop r sulphate per gallon. The cock was condiieted at a pressure of about pounds, at a temperature of 327 F. This high pressure was maintained onlyabout 25 minutes, although the 'liquid through the beater in the manner above indicated, for 45 minutes. At the commencement'of this time the roll was raised =five from the bed and b lowerin roll, a ittle at a time, at t e end 0 the period the roll was about one-half a turn 'bove the bed. The material was then divided into portions. One rtion was sheeteet of ed into the form of mold pulp, roduc-fl.

ing a light yellow-brown p p.

the

light washing, was made into paper, producing a very strong and relatively light colored paper of good strength and appear.- ance. A sheet of this paper having a thickness of .007 inch was tested and found to have a strength of 80 pounds (Mullen test). A sheet .003 inch thick tested 48 pounds and a sheet .004 inch thick tested 55 pounds.

In this example, the period of time, when the temperature of the liquor in the digester was above 212 F., was considered as the cooking period, and this amounted to about 2 hours. t

Example 3. Hickory wood was digested in, a solution containing about '1 ounce each of iron sul-' strength of 55 pounds. The entire operation, from the raw wood to the'sheeted pulp, occupied approximately 3 hours.

- Example 1,.

Oregon fir was treated with a solutioncontainine' about one and one-half ounces of potasslunl sulphate, per gallon of liquor. The sheeted material had a grayish color and was moderately strong.

E sample 6.

Marsh growth, largel s'edg es, was digested in a 1.5% solution 02 magnesium sulfate, and run through the beater. This was then, without washing, made into paper of Iabout the thickness of ordinary wrapping pa er. The productwas very strong, tough and exible. The pressure in the cooking was arou d 30 pounds, and the total cooking time (te perature o'ver 210 F-.,) was about an hour. r

Ewampleb.

The stalks of hop vineswere digested in' a solution containing 1% of magnesium sulfate and 5% of sodium sulfate, as in. the previous example. A good quality-of pulp was produced. l

E mample 7.

per gallon. I

Other woods, which have been used with good results are the following, red maple,

oaks, holly, sycamore, dogwood, long leaf pine, short leaf pine, old field pine, gum,

' like, a temperature notover280 F., and a pressure between and pounds give cx cellcnt results.

\Vith the cane and bamboo, the pressures and times may be about the same as for the woods. I

The process has given extremely good resalts with mixtures of cane and wood.

Example 8.

' about minutes; this pressure was main-.

tained for an,hour, and the heat then shut off, allowing to cool to about 5 pounds pressure in 75 minutes, the liquor blown out and the cooked material removed and thrown into cold water overnight. The material was then run through a pulp'er of themill-feed type, with water, then was beaten. for an hour in a standard beater. A part of this was sheeted forming an extremely strong carton stock, of a rather light tan color. This material was shown to be excellent for shoe counters etc.,-being about double the strength of the best high rade board stock on the market. High gra e board (the best grade found by me onthe market) of a thickness of .035 inch, tested 190 pounds,

while a product made by the-present example, from green cane and green short leafed pine, of the same thickness tested 385 pounds Another sheet of this latter material, .01 inch thick, tested 195 pounds.

' In another case, I digested green cane material (3parts) with Na. ,SO solution (3%) and mixed this with green pitch pine (about 1 part) digested in CuSO solution (2%) giving a very strong material for carton stock, shoe counters, etc. In other cases of green cane stock di ested with -K SO solution was mixed wit green gum stockdigested with Na sO C1130 FeSO or mixtures of these. In such mixtures 65 to of the canematerial was used with 25 to 35% of the .wood materiaL- I also find that good results" can be secured by mixing cane pulp with wood pulp, the latter being made by the'soda process, sulfite process or the old so called"sulfate process.

I call attention also to the fact that in the treatment of wood chips, it is-possible to add from ten to twenty per cent or so of saw dust or any other wood waste in the digester whereby the cost of the finished pulp can be materially-lowered.

There appears to be asubstantial advan tage of using woods, cane, grasses, marsh growths, etc., in the green state, rather than wholly dried, inthat stronger products are generally produced. The complete drying of thefmaterial, before cooking, seems to weaken the fibers, to some extent at least. Plant growths in either the green or dried condition can be readily reduced by my process.

As the result of my researches,'.the magnesium sulfate, alone or with alkali metal sulfate, as well as solutions of zinc sulfate with alkali metal sulfate, appear to give better results with grasses, bamboo, etc., than with resinous woods. Both of these give good results with the, non-resinous woods.

Sodium sulfate alone, or mixed with metallic sulfates seems to give better results with fir, spruce and hardwoods. Potassium sulfate alone or mixed with metallic sulfates seems to give better results with grasses, straw, bamboo, various stalks and marsh growths. These latter are apparently better treated with magnesium sulfate or with this plus an alkali metal sulfate. Aluminum sulfate alone or mixed with alkali metal sulfates reduces allplant growths well, but particularly with some of thd woods, seems to harden the fibers to some'extent. Tests also have shown that chromium sulfate givessomewhat darker colors to wood fibers and this material also colors some of the individual fibers from other growths as herein mentioned. Mild solutions of chromium sulfate give less darkening than strong solutions thereof (within the range of strengths herein referred to).

In digesting wood, there is sometimes an advantage in using sodium sulfate alone,

rather than potassium sulfate, magnesium I ktemperature of 337 F., with a pressure of 100 pounds, and it seems to be best not to exeeed a temperature of 320 F., with a pressure of 85 pounds. With grass s, particularly, very favorable results ar produced when the temperature does not exceed 280 F., with a pressure not over 35 pounds.

With woods, pressures not over 140 and best not over 125 pounds, are preferred.

- When magnesium sulfate is to be used as the largest saline constituent of the'digestive solution, it is advisable'when digesting cane,

grasses, marsh growths, etc., to use some K SO with this (say an amount equal to at been used in several successive cooks.

least 8%, and preferably up to 12%, of the weight of the MgSOQ. This,tends to keep the silica in suspension. \Vith woods, and especially the resinous woods, it is advisable to add about this proportion of sodium sulfate. In the case of the cane, grasses, etc., the material works freer on the screens, especially if the digestive solution has already This prevents the formation of gelatinous silica whi'clrwould clog the screens.

Example .9. The following example is given of Epsom salt (l\ lgSO .5' H O), alone as the digestive solution.

Green pitch pine in the form of blocks 3 inches long, 1 inch wide and 8 inches wide were filled into the digester in a basket or cage, and acold solution containing 2% of the crystallized salt run in. The cook was I heated until a pressure of 100 pounds showamount of wood.

ed in the I digester, (requiring about 105 minutes heating). This pressure was held for 45 minutes and the contents then allowed to cool to about. atmospheric pressure. The blocks were then run through a roller mill, then with water run through a pulper, and heated an hour. The yield was about 82%. This gave a strongfpulp.

lVhile I usually prefer to employ some N a. .SO'., or K SO,with the MgSO satisfactory results can be secured with the latter alone, especially when it is not desired to use the same cooking liquor for more than two or three cooks.

In most of the work done thus far, I have usedfreslr water inwhich to dissolve the sulfates. However, I note that salt water,

(e. g., sea water) can 'be used if desired, and

Example 1, 7 gallons of the sodium sulphate liquor, containingabout 1.8 ounces of sodium sulphate er gallon, to 10 lbs. of wood, will correspond to about .78 lbs. of the sulphate for each 10 lbs. of wood, or the amount of chemical .is about 7.8%, based on the Likewise in Example 2, the proportions given (assuming the same ratio of wood to chemical, on the amount of wood;

In Example 8, a somewhatv stronger solution was used, but a smaller amount thereof.

Thus a gallon of liquor. containin 3' ounces of salts, 2 lbs. of cane and W0 will correspondto about 7.5% of chemical relative to the wood, cane, etc.

The strength of solutions, as above given, are those which have been found to give excellent results. The solutions can be somewhat weaker, or stronger, without departing from the invention. For most purposes it is advisable not to employ less than half an ounce per gallon nor substantially more than four ounces per gallon. Stronger solutions are wasteful, and in some instances might considerably injure the product. I

The expression soluble sulfate of a metal having an atomic weight between 23 and 39.1as used herein, is intended to embrace the sulfates of sodium, magnesium, aluminum and potassium, hereinabove mentioned, as well as mixtures containing'one or more Y of these.

1 claim:

1. In the manufacture of pulpfrom cellulosic and ligueous material, the improvement which comprises digesting such. material with a solution of an alkali metal sulfate, substantially free from sulfid andsubstantially free from mineral acids.

2. 1n the manufacture of pulp from cellu losic and ligneou's material, the improvement which comprises digesting such material with a solution of an alkali metal sulfate together with another sulfate such solution. being substantially free front caustic alkali.

' 3.'In the manufacture of pulp from cellulos'ic and ligneous material, the improvement which comprises digesting such material with a solution containing an alkali metal sulfate, as substantially its only dissolved active inaterial, such solution con .taining one-half to five ounces of sulfate per gallon of liquor. Y

4 A process which comprises cooking lniittures of wood material and cane material, and sawdust and similar wood waste, in a hot digestive fluid containing an alkali forming metal sulfate as its principal active dissolved material, suchsolution being free from free caustic alkaliand from sulfids and .from sulfurous acid, and being of .a strength A process of making pulp which com-- prisps digesting in a cooking liquor contaimng not substantially over 4%rofa sulfate, a. mixture of chips .with up to 20% of saw-dust andother small wood waste, 'such solution being free from substantial amounts of free mineral acid. I 6.I In the treatment of cellulosic material,

the step of digesting the same with a solution containing a readily soluble sulfate of an alkali-forming metal, of substantially below 4% strength, such solution bein from substantial amounts of free mmeral acid. 7

' 7. In the treatment of cellulosic and ligneous material, the step of digesting the same with a solution containing a readily -soluble sulfate of an alkali-forming metal, in amount corresponding to about 1 to 4: ounces per gallon of liquor, such solution being free from substantial amounts of free mineral acid. v

8. In the treatment of cellulosic and ligneous material, the step of digesting the same with a solution containing magnesium sulfate and a sulfate of an alkali metal.

9. A process which comprises cooking mixtures of wood material and cane material, in a digestive'fi-uid.

10. A process which comprises cooking green cellulosic and ligneous material in a solution of an alkali-forming metal sulfate of 1 to 4%strength.

11.-A process which comprises digesting cellulosic and ligneous material, while hot and under pressure, with asolution containing a soluble sulfateof a metal having an atomic weight between 23 and 39.1, such solution being substantially free from, caustic alkali, .free from, "alkali-metal sulfids, and free from sulfurous acid.

12. The herein described process which comprises subjecting a cellulosic material to a cooking treatment by digestin the same in a solution, under superatmosp eric ressure, and at near the boiling point 0 the solution for the existing pressure, such solution containing a readily soluble alkaliforming metal sulfate as its principal dissolved active component, but such solution bein free from substantial quantities of .cellular cementitious matter in such cellulosic-material is rendered friable throughout the pieces of such material, whereby the said pieces, although retainin their original form, become] capable 0 being readily crushed, and thereafter reducing the mate-- rial to a pulp.

13: The herein described process which comprises subjecting pieces of wood of any kind to a cooking treatment by digesting the same in a solution ata temperature at which such solution boils under the existing pressure, said solution containing a sulfate of'a metal having an atomic weight between 23 and 39.1, such solution being free, from substantial amounts of sulfurous acid, until the. cementitious matter in such cellulosic material is rendered readily friable throughz out the pieces of such material, and stopping the di estion while the said pieces still retain t eir original form, but have become free in a hot solution containin sulfite and hydroxid, until the inter-' capable of being readily crushed, and thereafter reducing the material to a pulp.

14. The herein described process which.

comprises subjecting a cellulosic material to acooking treatment by digesting the same a sulfate of a metal having an atomic we1ght between 23 and 39.1, such solution being free from substantial amounts of sulfurous acid, until the cementitious matter in such cellulosic material is rendered readily friablethrou bout the pieces of such material, and until the said pieces, although retainin their original form, become capable of ein readily crushed, and thereafter mashing t e pieces of such material.

15. The herein described process which comprises subjecting a cellulosic material to 'a cooking treatment by digesting the same in a hot solution containing a sulfate of a metal having an atomic weight between 23 and 39.1, such solution being free from substantial amounts of sulfurous acid, until the cementitious matter in such cellulosic material is rendered readily friable throughout the pieces of such material, and until the said pieces although retainin their original form, become capable of icing readlly crushed, soaking the cooked material in water and thereafter mashing the same.

16. A process which comprisesdigesting cellulosic and ligneous material in the form of pieces much larger than the commonly used wood chips, in a solution containing .ametal sulfate, which solution is of a forming metal sulfate, which solution is of a strength not substantially above 3%, and being substantially free from zinc salts,

caustic alkali, soluble sulfides and sulfurous acid, continuing such digestion until the in tercellular cementitious material is rendered readily friable, but not until the said pieces of wood are substantially broken up or reduced to a pulp, and thereafter crushing such digested wood while wet, without grinding the same, and thereafter reducing the crushed wood with water to a pulp.

. l8. A process which comprises digesting woody'material in a solution containing a entitious matter is rendered friable but stopping the digestion while the pieces of 10 woody material still have substantially their original size and shape, and thereafter crush- .ing the digested material while still wet, and

reducing it to a pulp.

In testimony whereof I aflix my signature.

ROBERT A. MARR. 

